Increased GABAergic transmission in medial hypothalamus facilitates lordosis but has the opposite effect in preoptic area.
The role of gamma-aminobutyric acid (GABA) in mediation of lordosis in the rat has been unclear. We report here that GABA plays a dual role in the mediation of lordosis and has differential effects in the medial hypothalamus (MH) and preoptic area/anterior hypothalamus continuum (POA-AH). Bilateral infusion of the GABAA antagonist bicuculline into the MH of cannulated females primed with estradiol benzoate and progesterone (EB + P) resulted in a marked and transient inhibition of ongoing lordosis. A similar pattern of inhibition was seen in females treated with EB only. In contrast, infusion of the same dose of bicuculline into the POA-AH of sexually receptive females had no effect on lordosis whereas infusion of the GABAA agonist muscimol into this site resulted in a short-term inhibition of lordosis. Furthermore, when females were treated with subthreshold doses of EB + P to induce a low level of lordosis responding, infusion of muscimol into the MH resulted in a significant enhancement of lordosis; infusion of bicuculline into the POA-AH also enhanced lordosis responding as compared to saline-infused controls. These data indicate that increased GABAergic neurotransmission in the MH facilitates lordosis whereas increased GABAergic activity in the POA-AH inhibits this behavior.
McCarthy
M M
MM
Institute of Animal Behavior, Rutgers State University of New Jersey, Newark 07102.
Malik
K F
KF
Feder
H H
HH
D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D005260:Female; D007033:Hypothalamus, Middle / Q000187:drug effects / Q000502:physiology*; D009118:Muscimol / Q000494:pharmacology; D011187:Posture; D011301:Preoptic Area / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012726:Sexual Behavior, Animal / Q000187:drug effects*; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D009118:Muscimol; D005680:gamma-Aminobutyric Acid; D001640:Bicuculline